322 Reviews—Professor J. W. Gregory's Fossil Bryozoa. 
became important in the Upper Cretaceous, and it is the predominant 
group of Bryozoa in existing seas. 
Under ‘‘ Descriptive Nomenclature”’ the author defends his use of 
the term ‘gonocyst’ for a peculiar type of ovicell in some of the 
Cyclostomata on the ground that it differs from a ‘ goncecium’ in not 
being due to the modification of a single zocecium; but Dr. 8. F. 
Harmer, who has worked so extensively on the development of 
existing Cyclostomatous Bryozoa, raises the objection that in all 
Cyclostomata the ovicell is probably a modified zocecium, and therefore 
declines to accept the term proposed. Dr. Gregory further introduces 
the word ‘epizoarium’ instead of ‘epitheca’, borrowed from the 
nomenclature of corals, which is considered unsuitable as there is no 
theca in Bryozoa, and the layer is more important and varied in its 
functions in this latter group than in corals. ‘Cancelli’ is another 
term to which different meanings have been attached; by some it refers 
to aborted zocecia in dimorphic zoaria; these, however, are now named 
‘mesopores’ by Dr. Gregory, and cancelli are defined as “‘ spaces of 
interzocecial origin which remain either as simple or branched tubuli, 
or as macule, round spots or spaces, in the walls of the zoccia”’. 
But in certain cases, as in the Discoporellide (Lichenoporide) for 
example, there is great difficulty in determining whether the small 
pores are of the nature of ‘ cancelli’ or ‘mesopores’ : if the former, the 
family would be placed in the C. Cancellata; if the latter, in the 
Trepostomata ! 
Dr. Gregory then gives a general sketch of the various classifications 
proposed for the Cyclostomata by the principal authorities on this 
group from D’Orbigny onwards, and remarks that it shows an 
unusually complete divergence of opinion as to the number of’ sub- 
divisions required and as to their respective affinities. The summary 
of fifty years’ work indicates that a more complex classification is 
necessary for the fossil fauna than for the living members of the 
group. It would be possible to work out several different classifications 
of the Cyclostomata according to the values placed on the various 
characters. ‘‘Thus the nature of the zoarium, the general shape 
of the zocecium, the linear, radial, or irregular arrangement of the 
zocecia, and the solid or cancellous structure of the skeleton, might 
each be used as the primary systematic character.” Until more is 
known of the succession and geological distribution of the various 
forms, any classification of the Cyclostomata must be considered as 
experimental. That adopted by the author as the most suitable is 
based partly on zoarial and partly on zocecial characters, the former 
being used generally for the families and genera and the latter for 
the sub-orders. Three chief types of zocecia are recognized— 
(a) Simple, tubular, monomorphic zocecia with solid walls. 
(6) Zocecia monomorphic, having walls perforated by cavities—the 
cancelli. 
(ec) Zocecia dimorphic, one set being aborted to form supporting 
elements in the zoarium. 
The author is of opinion that the recent zonal collecting in the 
English Chalk by Dr. Rowe and others shows that the Bryozoa 
